Porous collagen anastomotic cuff

ABSTRACT

A tubular prosthesis useful in the anastomosis of blood vessels is prepared by weaving collagen strands to form a tubular fabric and immersing this structure in an aqueous acid solution containing acid-swollen collagen fibrils to swell said collagen strands. The tubular structure is then removed from the swelling solution and lyophilized to form a sponge-like tubular structure.

U ited States Patent Inventor Richard L. Kronenthal Fair Lawn, NJ. 713,325

Mar. 15, 1968 June 28, 1971 Ethicon, Inc.

Appl. No. Filed Patented Assignee POROUS COLLAGEN ANASTOMOTIC CUFF 4 Claims,6 Drawing Figs.

US. Cl 128/334, 3/1, l28/296 Int.Cl ..A6lb 17/11 Field of Search 128/334, 335, 335.5, (Collagen digest), 296; 3/l; 106/122, 155

[56] References Cited UNITED STATES PATENTS 3,443,261 5/1969 Battista et al. 3/] 2,610,625 9/1952 Sifferd et al. 128/296 3,157,524 11/1964 Artandi l28/296X OTHER REFERENCES Peacock et al. Annals of Surgery Feb 1965 pp 238- 247 Primary Examiner-Dalton L. 'l'ruluck Atmrneys- Robert W. Kell and Alexander T. Kardos ABSTRACT: A tubular prosthesis useful in the anastomosis of blood vessels is prepared by weaving collagen strands to form a tubular fabric and immersing this structure in an aqueous acid solution containing acid-swollen collagen fibrils to swell said collagen strands. The tubular structure is then removed from the swelling solution and lyophilized to form a spongelike tubular structure.

l POROUS COLLAGEN ANASTOMO'I'IC CUFF BACKGROUND OF THE INVENTION The present invention relates to a spongelike, porous collagen structure having exceptional tensile strength and tear strength. Moreover, the collagen sponges of the present invention are exceptionally resistant to suture pullout and are useful in surgery where they serve as an absorbable, resilient structural support having hemostatic characteristics.

A technical problem that frequently arises during the implantation of synthetic vascular grafts involves suturing severely atherosclerotic host vessels. ,Anastomosis to such tissue is difficult, and subsequent disasterous hemorrhage may result. Excessive bleeding after clamp removal may also occur if anastomotic sutures disrupt. Acceptable surgical procedure to reduce these tendencies involves placing a piece of autologous artery or graft material around the host vessel and suturing this cuff and vessel together to reinforce the seal and the anastomosis. This procedure has the disadvantage of leaving a foreign body contacting the vessel surface which may promote fibrosis and cause varying degrees of stenotic occlusion. The use of autologous artery for this purpose is cumbersome.

DESCRIPTION OF THE PRIOR ART Collagen sponge has been evaluated for anastomotic wrapping primarily to reduce initial bleeding tendencies. Such sponges have not, however, possessed sufficient tensile strength to structurally reinforce a weakened vessel. Collagen sponges have also been used in the surgical treatment of lacerated liver surfaces, the porosity of the sponge permitting it to act as a hemostatic device. A disadvantage of the sponge structure that interfered with this use, however, was its poor tenacity, which would cause the retaining sutures to pull out of the sponge structure.

SUMMARY OF THE INVENTION It has now been discovered that the tenacity of a collagen sponge may be improved by weaving a fabric of collagen tape or multifilament-and swelling the collagen fabric in a dilute acid solution. In a preferred embodiment of the invention, the acid solution may contain swollen collagen fibrils. The swollen collagen fabric is then frozen to form ice crystals within the collagen mass and lyophilized to form a porous structure. The collagen fibrils that are present in the sponge structure are biaxially oriented, i.e., the fibrils are oriented in the direction of the collagen strands and, therefore, aligned in two essentially perpendicular directions. At the same time, the tensile strength and tear strength of the sponges prepared in this manner are significantly increased to that these products may be used as a structural support in surgery. Such collagen products may be tanned to alter their absorption characteristics either before-swelling or after lyophilization.

EXAMPLE I A flat 0.62 inch inside diameter tubular fabric is woven from extruded collagen tape with 102 picks per inch, dress warp 139 ends. The extruded collagen tape is prepared in accordance with Example X of U.S. Pat. No. 3,114,372 by extruding the collagen dispersion through a stainless steel spinneret drilled with 140 openings and has a'denier of 180. I

The tubular collagen fabric is placed on a TEFLON mandrel having a diameter of 10 mm. and swollen for 6 hours in a dispersion of swollen collagen fibrils obtained by diluting 400 parts of the collagen dispersion described in Example I of U.S. Pat. No. 2,920,000 with 200 parts of a 10 percent acetic acid solution and 2,600 parts of distilled water. During this swelling step, the collagen strands in the fabric are united throughout their area of contact to form a unitary structure. The mandrel and tubular fabric are then removed from the swelling dispersion, drained, and frozen at F. The frozen mass is lyophilized until dry (16 hours) and then vapor-tanned for 16 hours in a chamber which contains a tray of 1 percent aqueous formaldehyde.

The resulting tubular product is spongelike due to the formation of ice crystals during the freezing step and subsequent sublimation of the water. The spongelike collagen tube may be readily removed from the TEFLON mandrel and sterilized by irradiation for surgical use.

The product so obtained is self-supporting, flexible, and porous yet has a high tensile strength (both circumferential and longitudinal) and a high resistance to suture pullout. This product has utility in the anastomosis of blood vessels and the implantation of synthetic vascular grafts as a structural support, which also functions as a hemostatic device.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings which show, by way of example,

preferred embodiments of the inventive idea.

Referring now to the drawings:

FIG. 1 is a plan view of a fabric woven from extruded collagen multifilament;

FIG. 2 is an enlarged view of a single collagen multifilament I on the line 2-2 of FIG. 1;

FIG. 3 is a schematic representation of a highly magnified longitudinal section of a single collagen monofilament illustrating the orientation of the collagen fibrils in a direction parallel to the longitudinal axis of the monofilament;

FIG. 4 is a plan view of the fabric of FIG. I in an acid swollen condition; I

FIG. 5 illustrates a section of the lyophilized fabric of FIG. .4 as it appears when viewed under a microscope; and

FIG. 6 is a schematic representation of the relationship between a void in the collagen sponge structure of the present invention and the collagen fibrils adjacent thereto.

EXAMPLE I] An extruded collagen multifilament is prepared in accordance with Example XII of U.S. Pat. No. 3,] 14,372. This multifilament, which contains 192 individual filaments, is woven to form a fabric illustrated in FIGS. 1 and 2 having 102 picks per inch (dress warp 139 ends). In FIG. 1, the space between the warp threads 10 and the filling threads 11 is exaggerated to better illustrate the effect of subsequent swelling in acid solution. The spaces between the individual monofilaments 12 that make up the warp threads 10 is shown in FIG. 2. The orientation of the collagen fibrils 14 in the extruded filament prepared in accordance with Example XII of U.S. Pat. No. 3,114,372 is parallel to the longitudinal axis of the filament 12 as illustrated in FIG. 3. This fabric is secured on a frame and immersed in an aqueous swelling solution containing 4 percent by weight aqueous acetic acid. After 4 hours, the frame and fabric are removed from the swelling solution which is drained off. The acid-swollen fabric has the appearance illustrated in FIG. 4. The swollen fabric is frozen at 0 F. The product is then lyophilized until dry (14 hours) and vapor-tanned for 16 hours in a chamber which contains a tray of 1 percent aqueous formaldehyde. The tanned sheetlike collagen sponge so obtained is removed from the frame and cut into pieces of the desired size for surgical use and sterilized with Cobalt 60 radiation. A small sample of the tanned sponge is cut with a razor blade parallel to the warp so that the longitudinal aspect of the warp thread and the cross-sectional aspect of the filling threads could be examined under the microscope by reflected light. The voids 15 of the spongelike structure are present throughout the warp and filling threads as shown in FIG. 5. As best illustrated in FIG.6, the general alignment of the fibrils 14 parallel to the longitudinal axis of the filaments 12 is not significantly altered during the acid swelling and lyophilizationsteps. The collagen fibrils that are present in the sponge structure are biaxially oriented, i.e., the fibrils are oriented in the direction of the collagen filaments and, therefore, aligned in two essentially perpendicular directions corresponding to the axis of the warp threads and the axis of the filling threads. The sponge structure so obtained is porous but blood impermeable since clotting occurs in the air cells between the two outer surfaces of the sponge. The porous nature of this collagen structure makes is useful in surgery and most particularly in situations involving liver damage where the resiliency of the spongelike structure permits pressure to be applied against the bleeding surface. To some extend, the swelling that follows traumatic liver damage can be accommodated by the sponge which will expand again as the swelling subsides. In addition, the high tear strength of the spongelike structure makes it possible to use sutures in tying the sponge tothe liver surface.

lclaim:

1. A surgical prostheses useful as an anastomotic cuff in the surgical repair of blood vessels comprising a porous tubular collagen sponge consisting essentially of rectilinear collagen fibrils about one-half of said fibrils being oriented only in a direction parallel to the longitudinal axis of the tubular sponge and the remaining fibrils present in said structure being oriented only in a direction perpendicular to the longitudinal axis of the tubular sponge, said sponge structure being impermeable to blood and being characterized by a high tensile and tear strength.

2. The surgical prosthesis of claim 1, which has been tanned to increase wet tensile strength and reduce the rate of absorption in living tissue.

3. A surgical prostheses useful in the surgical repair of liver tissue comprising a porous, flat, collagen sponge having a longitudinal axis and a transverse axis parallel to the surface of the sponge said sponge consisting essentially of rectilinear collagen fibrils, about one-half of said fibrils being aligned only with said longitudinal axis, the remaining fibrils present in said structure being aligned only with said transverse axis, said sponge structure being impermeable to blood and being characterized by a high tensile and tear strength.

4. The surgical prosthesis of claim 3, which has been tanned to increase wet tensile strength and reduce the rate of absorption in living tissue. 

